Replacement of halogen spotlighting lamps by LEDs is a growing market. Replacing halogen lamps by LEDs is quite challenging since halogen lamps and LEDs have different properties. More specifically, a difference between halogen lamps and LEDs is that LEDs have a limited flux output in comparison to halogen lamps. In order for a LED spotlight to have the same maximum intensity at specific beam angles as a halogen spotlight, the optics of the LED spotlight therefore needs to provide a much higher intensity in the center of the beam per unit flux in order to compensate for the limited flux output. The intensity in the center of the beam per unit flux is often referred to as center beam candle power (CBCP) per lumen value, or simply Cd/lm or CBCP/lm.
In view of the above, it is thus a challenge in LED spotlighting optics to design a compact and efficient optics in a very limited space to get a higher CBCP/lm value for specific beam angles.
LED spotlighting optics typically comprise a total internal reflection (TIR) collimator having an opening for receiving a LED, and a central convex lens which is arranged at a distance from the opening where the LED is received. However, with such an arrangement it is difficult to collimate and redistribute the light coming through the central convex lens because the lens is positioned too close to the LED source whose size is negligible. Due to this limitation of the central lens, the light intensity distribution of the output light beam gets undesirably heavy tails and thereby it is difficult to get certain beam pattern having high CBCP/lm values at specific full width half maximum (FWHM) beam angles. The FWHM beam angles are defined by the angles relatively the center of the beam for which the light intensity is half the light intensity of the center of the beam.